CODEWITHSUNDEEP
c#datatable
Xavier Dennis
Xavier Dennis

Reputation: 39

Invalid usage of aggregate function Sum() and Type: String

I have a data table and a column contains int values. I have not specified the column with any datatype. When I perform the following.

object sum = dttest.Compute("sum(Value)", "");

I am getting below error.

Invalid usage of aggregate function Sum() and Type: String.

And I tried converting column value to int using

object sum = dttest.Compute("sum(Convert(Value, 'System.Int32'))","");

again I am getting another error

Syntax error in aggregate argument: Expecting a single column argument with possible 'Child' qualifier.

When I specify the datatype for the column, first code will return correct value. But in my case I can't specify column datatype. Any one having solution ?

Upvotes: 2

Views: 25093

Answers (4)

Balan
Balan

Reputation: 421

When the program try it sum a datatable column which declared as string this error occur.
Use the below code to make compute operation on string column.

dtTable.Compute("Sum(Convert(" + col_Name + ", 'System.Int32')","");

Upvotes: 0

Damith
Damith

Reputation: 63065

try

object sum = dttest.Compute("Sum(Value)", "[Value] IS NOT NULL");

Sample code 

    static DataTable GetTable()
    {
        DataTable table = new DataTable();
        table.Columns.Add("Value", typeof(int));
        table.Columns.Add("Name", typeof(string));
        table.Rows.Add(null, "a");
        table.Rows.Add(50, "a");
        table.Rows.Add(10, "a");
        table.Rows.Add(21, "b");
        table.Rows.Add(100, "b");
        return table;
    }
    static void Main(string[] args)
    {
        DataTable dt =GetTable();
        var str = dt.Compute("Sum(Value)", "Name='a' and Value is not null");
    }

You can't Call Sum with Convert, but you can try below 

DataTable dt =GetTable();
dt.Columns.Add("temp", typeof(int), "Convert(Value, 'System.Int32')");
var str = dt.Compute("Sum(temp)", "Name='a' and Value is not null");

Upvotes: 1

cuongle
cuongle

Reputation: 75306

You can use LINQ to Datatable:

 var result = dttest.AsEnumerable()
                    .Sum(x => Convert.ToInt32(x["Value"]));

Example how to Sum for specific name:

 var result = dttest.AsEnumerable()
                    .Where(r => r.Field<string>("Name") == "FilterName")
                    .Sum(x => Convert.ToInt32(x["Value"]));

Upvotes: 10

kostas ch.
kostas ch.

Reputation: 2035

try

dttest.Compute("Sum(Convert([Value], 'System.Int32'))","[Value] IS NOT NULL");

Upvotes: 0

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